An electrostatic discharge (ESD) event refers to a momentary current surge flowing to, from, or within a circuit, where the momentary current surge has an excessive amount of current and may cause damage to the circuit. Many electrical circuits and devices are susceptible to damage caused by ESD events. ESD protection circuits are usually implemented in a chip to protect the devices and circuits on the chip from ESD damage. Operations of ESD protection circuits generally include one or a combination of the following mechanisms: dissipating the ESD current using a low-impedance discharging path, clamping an ESD induced voltage to a predetermined safe level, and etc.
Like reference numbers in the various drawings are used to indicate like elements.